1. Field of the Invention
The present application relates to a method for effectively using power resources in a wireless mesh network capable of effectively selecting and changing a power saving mode of mesh terminals constituting a wireless mesh network according to a terminal and network situation, to thus reduce the power consumption of respective mesh terminals and maintain optimal network performance.
2. Description of the Related Art
A wireless mesh network is a network technique that provides a service such as Internet access or the like to multiple user terminals through multi-hop communications among wirelessly connected mesh routers.
Unlike a base station-centered mobile communication network or a hotspot-centered wireless local area network (WLAN), the mesh network transfers data through wireless multi-hop communications among mesh routers, having an advantage of facilitating a network extension and maintenance. Recently, diverse standardization groups, including IEEE 802.11s which is a group concerned with WLAN standards, have been working to try to introduce such a mesh network function.
The IEEE 802.11s standard has proposed a hybrid wireless mesh protocol (HWMP) for multi-hop routing. The HWMP protocol uses both a routing scheme in an on-demand AODV format (i.e., an AODV format based on a demand) and a scheme that periodically manages a routing path in a tree form. In order to manage the routing path in the tree form, a single root terminal exists in the network and periodically transmits a root announcement message to the entire network. In addition, a power saving mode is divided into a light sleep mode and a deep sleep mode to reduce the power consumption of a mesh terminal. A mesh terminal operating in light sleep mode periodically transmits a beacon frame and informs neighboring terminals that it has data to be transmitted via TIM information existing within the beacon. The mesh terminal operating in light sleep mode receives all the beacon frames from neighboring terminals, and if there is no data sent to the mesh terminal, the mesh terminal may turn off its transmitting/receiving device. However, in the case that there is data to be transmitted to the mesh terminal, the mesh terminal does not turn off the power of the transmitting/receiving device and receives the data. A mesh terminal operating in deep sleep mode does not need to receive the beacon frames of the neighboring terminals but receives only a DTIM beacon with a longer period. If a particular terminal has data to be sent to the mesh terminal operating in the deep sleep mode, it transmits the DTIM and then transmits the data to the mesh terminal while the mesh terminal is active. Except for this time duration, the mesh terminal operating in the deep sleep mode can always turn off its transmitting/receiving device's power, saving power resources.
However, the current standard does not define any substantial operating method concerning switching conditions between the both modes, namely, when deep sleep mode is to be used and when light sleep mode is to be used. If each terminal selects its mode one-sidedly without considering its relationship with the other network terminals and its own network connection status, side effects such as an increase in a delay time of the network and a reduction in throughput would be generated to end in a reduction in the existence duration of the network. Thus, a technique that can select a power saving mode of mesh terminals in consideration of these aspects is required.